Although it has long been known that the sun is a virtually inexhaustible energy source, very little serious effort has been applied to practically utilizing solar energy. Recently, however, as fossil fuel sources have proven to be inadequate to meet present demands for energy, more attention has been given to the problem of depleting the supply of fossil fuel within the foreseeable future. It has become apparent that alternative energy sources must be developed.
Substantial effort has been made in the field of energy production using nuclear energy sources. However, the quantity of nuclear material is also limited and many experts consider nuclear energy a stop-gap solution at best. Conversion of solar radiation into usable energy appears to be an ultimate solution to our long-term energy requirements.
Not only is solar energy virtually inexhaustible, it is clean and produces no polluting wastes or by-products. Even in geographical areas where cloud cover makes solar energy conversion ineffective, electricity which was produced elsewhere by solar energy conversion could be utilized.
The earliest attempts to utilize solar radiation were directed to apparatus for raising water for irrigation purposes. Such a system was described in 1890 in U.S. Pat. No. 433,055 issued to C. Tellier. The patents of Aubrey G. Eneas were obtained in 1900 and described a solar powered steam engine "especially intended for use in connection with irrigation of the grid plains of the West."
Until the advent of electricity, such energy producing systems were relatively inflexible. They were effective only during sunlight hours and only to produce work in the vicinity of the solar conversion apparatus. Conversion of solar radiation into electricity permitted the converted energy to be transported and stored. In 1921, W. J. Harvey disclosed a refinement in U.S. Pat. No. 1,386,781 for tracking the sun to permit utilization of the maximum available energy during sunlight hours. Since this system utilized a clockwork mechanism, it was necessary to periodically adjust and verify the tracking course to compensate for the progression of the sun's track across the sky throughout an annual cycle.
The problem of balancing a constant energy generating system against a variable energy demand was attached by A. Weipel. In his 1965 U.S. Pat. No. 3,214,915, he disclosed a system in which a constant output hydroelectric generator is used in a variable demand arrangement. During peak demand periods, all electricity produced by the generator is applied to a customer distribution network. When customer demand goes down, the excess electricity is used to power a hydraulic pump which raises water from a low-lying reservoir to a reservoir at an elevated location. Later, the potential energy thus stored is recovered by the action of water from the elevated reservoir in powering the hydroelectric generator.
However, no system is perfectly efficient and it is always necessary to compensate for losses in the system. If the Weipel system is placed where there is significant rainfall, the natural runoff could provide such compensation if it were collected in the elevated reservoir. However, in sunny, arid regions the compensating effect of rainfall is minimized. In fact, because of increased evaporation in arid regions, such a system would have increased losses in such a setting.
Prior systems for collecting and concentrating solar radiation have been of two general configurations, planar and deep-dish. The planar collectors have been inefficient because of the relatively large reflective losses produced by radiation reflecting away from their surface. Deep-dish configurations have been effective in minimizing reflective losses, and in concentrating collected radition. However, the intricate shape, such as parabolic surfaces, makes such deep-dish collectors expensive to fabricate. For example, the United States Army's 80-foot diameter collector at White Sands, New Mexico, cost almost a million dollars and a larger one fabricated by the French in 1970 cost twice that much.
Systems for directly converting solar energy into electricity are not new; but they are very expensive. Solar cells produce electricity at a cost that is prohibitive, up to one hundred times the cost of electricity produced by a coal-fired generating plant.
It is therefore an object of my invention to produce electricity converted from solar energy at a low, competitive cost.
It is also an object of my invention to produce an electrical generating system having a generating capability unrelated to demand with storage capacity for energy generated in excess of demand.
It is a further object of my invention to produce an energy storage system using solar radiation as principal energy input and compensation for loss and operational inefficiency.
Yet another object of my invention is to produce a solar radiation conversion system that will automatically track the sun so that the maximum solar effect may be realized at all times.
Still another object of my invention is to produce a solar radiation collector having a simple, economically produced and highly efficient configuration.